1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
/*
* Copyright 2010-2015 Samy Al Bahra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef CK_BYTELOCK_H
#define CK_BYTELOCK_H
/*
* The implementations here are derived from the work described in:
* Dice, D. and Shavit, N. 2010. TLRW: return of the read-write lock.
* In Proceedings of the 22nd ACM Symposium on Parallelism in Algorithms
* and Architectures (Thira, Santorini, Greece, June 13 - 15, 2010).
* SPAA '10. ACM, New York, NY, 284-293.
*/
#include <ck_cc.h>
#include <ck_md.h>
#include <ck_pr.h>
#include <ck_stdbool.h>
#include <ck_stddef.h>
#include <ck_limits.h>
struct ck_bytelock {
unsigned int owner;
unsigned int n_readers;
uint8_t readers[CK_MD_CACHELINE - sizeof(unsigned int) * 2] CK_CC_ALIGN(8);
};
typedef struct ck_bytelock ck_bytelock_t;
#define CK_BYTELOCK_INITIALIZER { 0, 0, {0} }
#define CK_BYTELOCK_UNSLOTTED UINT_MAX
CK_CC_INLINE static void
ck_bytelock_init(struct ck_bytelock *bytelock)
{
unsigned int i;
bytelock->owner = 0;
bytelock->n_readers = 0;
for (i = 0; i < sizeof bytelock->readers; i++)
bytelock->readers[i] = false;
ck_pr_barrier();
return;
}
#ifdef CK_F_PR_LOAD_64
#define CK_BYTELOCK_LENGTH sizeof(uint64_t)
#define CK_BYTELOCK_LOAD ck_pr_load_64
#define CK_BYTELOCK_TYPE uint64_t
#elif defined(CK_F_PR_LOAD_32)
#define CK_BYTELOCK_LENGTH sizeof(uint32_t)
#define CK_BYTELOCK_LOAD ck_pr_load_32
#define CK_BYTELOCK_TYPE uint32_t
#else
#error Unsupported platform.
#endif
CK_CC_INLINE static void
ck_bytelock_write_lock(struct ck_bytelock *bytelock, unsigned int slot)
{
CK_BYTELOCK_TYPE *readers = (void *)bytelock->readers;
unsigned int i;
/* Announce upcoming writer acquisition. */
while (ck_pr_cas_uint(&bytelock->owner, 0, slot) == false)
ck_pr_stall();
/* If we are slotted, we might be upgrading from a read lock. */
if (slot <= sizeof bytelock->readers)
ck_pr_store_8(&bytelock->readers[slot - 1], false);
/*
* Wait for slotted readers to drain out. This also provides the
* lock acquire semantics.
*/
ck_pr_fence_atomic_load();
for (i = 0; i < sizeof(bytelock->readers) / CK_BYTELOCK_LENGTH; i++) {
while (CK_BYTELOCK_LOAD(&readers[i]) != false)
ck_pr_stall();
}
/* Wait for unslotted readers to drain out. */
while (ck_pr_load_uint(&bytelock->n_readers) != 0)
ck_pr_stall();
ck_pr_fence_lock();
return;
}
#undef CK_BYTELOCK_LENGTH
#undef CK_BYTELOCK_LOAD
#undef CK_BYTELOCK_TYPE
CK_CC_INLINE static void
ck_bytelock_write_unlock(struct ck_bytelock *bytelock)
{
ck_pr_fence_unlock();
ck_pr_store_uint(&bytelock->owner, 0);
return;
}
CK_CC_INLINE static void
ck_bytelock_read_lock(struct ck_bytelock *bytelock, unsigned int slot)
{
if (ck_pr_load_uint(&bytelock->owner) == slot) {
ck_pr_store_8(&bytelock->readers[slot - 1], true);
ck_pr_fence_strict_store();
ck_pr_store_uint(&bytelock->owner, 0);
return;
}
/* Unslotted threads will have to use the readers counter. */
if (slot > sizeof bytelock->readers) {
for (;;) {
ck_pr_inc_uint(&bytelock->n_readers);
ck_pr_fence_atomic_load();
if (ck_pr_load_uint(&bytelock->owner) == 0)
break;
ck_pr_dec_uint(&bytelock->n_readers);
while (ck_pr_load_uint(&bytelock->owner) != 0)
ck_pr_stall();
}
ck_pr_fence_lock();
return;
}
slot -= 1;
for (;;) {
#ifdef CK_F_PR_FAA_8
ck_pr_fas_8(&bytelock->readers[slot], true);
ck_pr_fence_atomic_load();
#else
ck_pr_store_8(&bytelock->readers[slot], true);
ck_pr_fence_store_load();
#endif
/*
* If there is no owner at this point, our slot has
* already been published and it is guaranteed no
* write acquisition will succeed until we drain out.
*/
if (ck_pr_load_uint(&bytelock->owner) == 0)
break;
ck_pr_store_8(&bytelock->readers[slot], false);
while (ck_pr_load_uint(&bytelock->owner) != 0)
ck_pr_stall();
}
ck_pr_fence_lock();
return;
}
CK_CC_INLINE static void
ck_bytelock_read_unlock(struct ck_bytelock *bytelock, unsigned int slot)
{
ck_pr_fence_unlock();
if (slot > sizeof bytelock->readers)
ck_pr_dec_uint(&bytelock->n_readers);
else
ck_pr_store_8(&bytelock->readers[slot - 1], false);
return;
}
#endif /* CK_BYTELOCK_H */
|
